Toothpastes

ABSTRACT

A toothpaste containing glycerine, water and chloroform, characterised by the inclusion as a corrosion inhibitor to inhibit the corrosiveness of the toothpaste to aluminium of urea, biuret, gelatine, benzoic acid or a salt of benzoic acid.

' United States Patent Venables et a1.

[ Dec. 16, 1975 TOOTHPASTES Inventors: Susan Mary Venables, Ascot;

Charles Andrew Watson, Ruislip, both of England Assignee: Lever Bros. Co., New York, NY.

Filed: Aug. 23, 1974 Appl. No.: 499,815

Related U.S. Application Data Division of Ser. No. 309,535, Nov. 24, 1972, Pat. No. 3,878,938.

U.S. Cl. 53/6; 206/84; 222/92; 222/106; 424/54 Int. Cl. A61K 7/22; A45D 40/00 Field of Search 424/54; 206/84; 222/92, 222/106; 53/6 References Cited UNITED STATES PATENTS 1/1936 Jacobson 424/49 2,059,396 11/1936 Ripert 424/58 2,588,324 3/1952 Lewis et a1 424/54 3,538,230 11/1970 Pader et a1 424/52 3,551,559 12/1970 Miles 424/49 FOREIGN PATENTS OR APPLICATIONS 1,225,816 9/1966 Germany 424/54 Primary ExaminerShep K. Rose Attorney, Agent, or FirmJames J. Farrell, Esq.

1 Claim, No Drawings TOOTHPASTES This is a division of application Ser. No. 309,535, filed Nov. 24, 1972, now US. Pat. No. 3,878,938, dated Apr. 22, 1975.

This invention relates to toothpastes.

Most toothpastes contain a proportion of water, the liquid phase consisting of a mixture of humectant and water. Glycerine and sorbitol are the most usual humectants, although others are occasionally used.

Chloroform is an ingredient commonly added to toothpastes for the purpose of improving the flavour. It is usually included in an amount in the range 0.5 to 4.0% by weight.

The inclusion of chloroform, however, can give rise to corrosion of aluminium tubes, aluminium being the most convenient and least expensive material for toothpaste packaging. It has been suggested to mitigate this corrosion problem by the use of relatively high levels of glycerine in the liquid phase of the toothpaste. However, the use of high levels of glycerine results in products which are of high raw material cost, have a stringy fracture and are slow to disperse in the mouth. The problem of tube corrosion due to chloroform arises when water is present in the toothpaste at more than about by weight of the liquid phase. The occurrence of corrosion is also especially marked at chloroform levels above about 1% by weight of the toothpaste. The problem of corrosion due to chloroform is one that has been known to toothpaste manufacturers for a long time.

It has now been found that corrosion of aluminium due to chloroform may be substantially reduced "in the case of toothpastes containing glycerine as humectant by including urea, biuret, gelatine or benzoic acid or a water-soluble salt of benzoic acid, or a mixture thereof, in the product.

Accordingly the present invention provides a toothpaste containing glycerine, water and chloroform having a reduced tendency to corrode aluminium comprising as corrosion inhibitor urea, biuret, gelatine, or benzoic acid or a water-soluble salt of benzoic acid.

The level of the urea, biuret, gelatine, benzoic acid or benzoic acid salt in the toothpaste required to give a corrosion inhibitive effect may be determined by exphase of the toothpaste. Furthermore, the higher levels of chlorofonn in the range 0.5 to 4.0% generally tend to produce greater corrosion. However, as stated, for a particular combination of levels of water and chloroform, it is merely a matter of simple experimentation to determine what level of the appropriate inhibitor is required to produce a substantial corrosion inhibitive effect.

A corrosion inhibitive effect is obtained in certain cases with a level of urea as low as 0.1% by weight of the toothpaste although generally an amount of at least 0.5% by weight and in the range 0.5 to 2% will be desirable. The chemically related compound biuret appears not to be quite so effective as urea on a weight for weight basis and biuret is recommended for use at a level of at least 0.5% by weight of the toothpaste, preferably an amount of from 1 to 2% by weight being used.

When using gelatine as the corrosion inhibitor, this material is desirably used at a level of at least 0.1% by weight of the toothpaste, the preferred amount being in the range 0.5 to 2%. Benzoic acid and its water-soluble salts are desirably used in an amount of at least 0.5% by weight of the toothpaste, the preferred levels for these inhibitors being from 1 to 5% by weight.

There is no advantage in using more of an inhibitor than is necessary to obtain the required reduction in corrosion. Amounts of corrosion inhibitor necessary are unlikely to be as high as 10% and usually will not need to exceed 5% by weight of the toothpaste.

Apart from the corrosion inhibitor, the dentifrice of the invention will comprise the usual ingredients in the usual proportions. Thus typically for a toothpaste in accordance with the invention, it will comprise, along with the corrosion inhibitor, preferably 15 to 40% by weight of glycerine, 30 to 60% by weight of an abrasive cleaning agent, 1 to 2.5% by weight of a surface-active agent, 0.5 to 4.0% by weight of chloroform, and the usual minor amounts of binding agent, flavouring agent and sweetening agent with the balance being water, the latter usually being present in an amount of about 8 to 30% by weight.

The following experiments illustrate the invention. Percentages are by weight.

Five base toothpastes were made having the following formulae:

*The amount of chloroform varied due to the volatility of chloroform.

periment. The amount required is related somewhat to the amount of water in the toothpaste. Increasing Other toothpastes in accordance with the invention were prepared by replacing a part of the abrasive by the amounts of inhibitor are required with the presence of 65 corrosion inhibitor.

greater amounts of water in the toothpaste. ln usual commercial practice the amount of water may vary from about 25% to about by weight of the liquid All the toothpastes were packed in unlacquered aluminium tubes and tested for corrosion by one or more of the following three test methods.

3 Test Method A Six tubes of the toothpaste under test were stored at 50C and 65C for up to 6 months and one tube of each TABLE 4-continued Storage time test product at each temperature was Opened every Toothpaste Biuret 7c of tubes perforated (months) month and the inner walls were examined for corro- 5 2 3 Sion Ill 0 89 2 2 0 2 Test Method B 4 0 2 216 and 72 tubes of the product under test were 1V stored at 50C and 65C, respectively, and were exam- 4 0 2 ined for external signs of tube corrosion, i.e., perforation of the tube, at various intervals. The percentage of the rziumber of tubes stored showing signs of corrosion The results Obtained by Test Methods B and C m s i i g? at each exammauon' trating the efi'ectiveness of gelatine as a corrosion ines e o lbltor are ven below in Tables 5 and 6, res ectivel Between 12 and 24 tubes of the toothpaste under test g p y were stored at 65C and were examined at monthly intervals for external signs of tube corrosion. The per- TABLE 5 centage of the number of tubes stored showing external f tubes f md ft signs of corrosion was determined at each examination. storage for 6 months The results obtained are given below. Tmthpaste (lemme at The results obtained by Test Methods A and B illusl 0 41 93 trating the effectiveness of urea are given in Tables 1 2 7 and 2, respectively.

TABLE 1 25 TABLE 6 Extent of corrosion after storage of tubes perforated after a! 65 C for? Toothpaste Gelatine storage for 6 months Toothpaste Urea 1 month 3 months 6 months I 0 93 l 0 moderate perforation perforation 0 5 1 8 0.1 slight slight sl ght n O 5 1 none very slight slight 10 "one 2 none none none 15 none 5 none none none I 5 none ll 0 moderate perforation perforation none 1 none none none In 0 88* 2 none none none 2 0 one ll] 0 perforation perforation perforation 2 none none none IV 0 slight severe perforation result after 2 months 2 none none none V 0 erforation erforation erforation 1 E E E The results obtained by Test Methods A, B and C illustrating the effectiveness of sodium benzoate as a corrosion inhibitor are given below in Tables 7, 8, and TABLE 2 9, respectively.

of tubes perforated after TABLE 7 Storage for 12 months Extent of corrosion after Toothpaste Urea at C at 65C Sodium storage at 50C for:

l 0 65 45 Toothpaste Benzoate 1 month 3 months 6 months [V 0 slight slight slight 2 O O 2 very none very slight slight V O slight perforation perforation 5O 2 slight very slight none The results obtained by Test Methods B and C illustrating the effectiveness of biuret as a corrosion inhibitor are given below in Tables 3 and 4, respectively. TABLE 8 of tubes perforated after TABLE 3 Sodium storage for 6 months f tubes f weeks Toothpaste Benzoate at 50C at 65C Toothpaste 7e Biuret perforated storage at 65 C l 0 41 93 l 0 83 14 2 6 42 2 21 14 II 0 34 53 3 l4 l4 2 1.5 31

TABLE 4 TABLE 9 S Toothpaste 7c Sodium Benzoate of tubes perforated after time stora e for 6 months Toothpaste Biuret 7: of tubes perforated (months) g i g m 0 88* ll 0 ll 3 5 20 Result after 2 months The results obtained by Test Method C illustrating the effectiveness of benzoic acid and a variety of watersoluble salts of benzoic acid as corrosion inhibitors are given below in Table 10. The results apply to the inclusion of the inhibitor at a level of 2% in Toothpaste I.

TABLE of tubes showing signs of corrosion after storage for 6 months While it has previously been pro osed to include in toothpastes urea and biuret (as t erapeutic agents), gelatin (as a binder) and sodium benzoate (as a preserving agent), the use of these materials as corrosion inhibitors in chloroform-containing toothpastes is believed to be original.

What is claimed is:

l. A process for inhibiting the corrosive action of a toothpaste containing chloroform on unlacquered alummum tubes comprising incorporating in said toothpaste an effective corrosion-inhibiting amount of a substance selected from the group consisting of urea, biuret, gelatine, benzoic acid and soluble salts of benzoic acid, said effective amount of urea and gelatine being within the proportions of about 0.1% to about 10%, and said efiective amount of biuret, benzoic acid, and soluble salts of benzoic acid bein within the proportions of about 0.5% to about 10%, y weight of said toothpaste, and packing said toothpaste containing said corrosion-inhibiting substance in an unlacquered aluminum tube. 

1. A PROCESS FOR INHIBITING THE CORROSIVE ACTION OF A TOOTHPASTE CONTAINING CHLOROFORM ON UNLACQUERED ALUMINUM TUBES COMPRISING INCORPORATING IN SAID TOOTHPASTE AN EFFECTIVE CORROSION-INHIBITING AMOUNT OF A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF UREA, BIURET, GELATINE, BENZOIC ACID AND SOLUBLE SALTS OF BENZOIC ACID, SAID EFFECTIVE AMOUNT OF UREA AND GELATINE BEING WITHIN THE PORPORTIONS OF ABOUT 0.1% TO ABOUT 10%, AND SAID EFFECTIVE AMOUNT OF BIURET, BENZOIC ACID, AND SOLUBLE SALTS OF BENZOIC ACID BEING WITHIN THE PROPORTIONS OF ABOUT 0.5% TO ABOUT 10%, BY WEIGHT OF SAID TOOTHPASTE, AND PACKING SAID TOOTHPASTE CONTAINING SAID CORROSION-INHIBITING SUBSTANCE IN AN UNLACQUERED ALUMINUM TUBE. 